The invention relates to gyratory crushers and particularly to the gyratory motion mechanism of gyratory crushers.
The invention may be best understood in consideration of generally understood operating characteristics of gyratory crushers. Gyratory crushers or cone crushers are those which support a cone-shaped crushing head capable of undergoing a gyrating motion centered generally about a vertical central axis through the crusher. The gyrating motion of the crushing head performs a crushing action on material which enters a space between the head and an inner surface of a concave or bowl-shaped stationary member. The bowl-shaped member is disposed in an inverted position generally over the cone-shaped crushing head. The bowl-shaped member is centered on the axis through the crusher and has a central opening through which materials, such as rock, ore, coal or the like are fed into the space between the crushing head and the stationary, bowl-shaped member. The action of the crusher typically distributes the materials annularly about the centrally disposed conical shape of the crushing head. The materials typical move by gravity into the annular space between the inner wall of the stationary bowl member and the outer, cone-like surface of the crushing head. The annular space between the bowl member and the crushing head is also referred to as the crushing chamber. The gyration of the crushing head causes the space at any specific radial position of the crusher to cyclically increase and decrease in width. The cyclic, relative motion of the two members comminutes the materials as they are drawn by gravity though the annular, downward sloping space to be discharged at the base of the crushing chamber.
Cone crushers are generally chosen to be optimally suited for specific operating conditions and materials. The shape of the crushing chamber, the angle of the conical head, the stroke (the difference between the extremes of gyratory movement of the crushing head), and the rotational speed of the gyratory drive are factors which are typically considered in the selection of a crusher. Selection of a crusher with optimum specifications including its size is often based on prior experience with the materials to be comminuted. For example, the hardness of rock or ore may limit the amount of reduction that can be achieved in a single path. Consequently, hard rock may require a stroke length on the short end of a range of typically specified gyration strokes. Such relatively short stroke may limit the material throughput rate or capacity of the crusher. On the other hand, a comparatively easier to crush or softer material or rock may permit a greater reduction during a single pass, hence a relatively longer stroke of the crusher may be specified. The relatively long stroke may, in general, also permit a greater material throughput.
For many commercial crushing applications, however, gyratory crushing plants are intended for use at many different locations. For example, road construction projects often require crushing operations at a number of successively accessed quarries. Each location may provide materials of different hardness. For crushers intended to produce under such variable conditions, it would generally not be possible to preselect operating specifications of the crusher to optimize the crusher for any particular source material. Instead, it appears desirable to have available a crusher which can be adjusted to work optimally with materials without much concern as to hardness or crushability. An ideal crusher would permit an operator to optimize crusher throughput and product quality at each new site, as for example by making sample runs and by fine tuning of certain adjustable operating parameters of the crusher.
For any given crusher size and type, the closed side setting (CSS) which is the least gap between the crusher head and the bowl, may not be less than a certain minimum setting at which the crusher begins to be overloaded. The CSS is typically adjustable by raising or lowering the bowl or stationary member with respect to the crusher head. According to some known crusher makes the crushing head may be raised or lowered to establish the CSS. The rotational speed of the crusher head may, of course, be changed. However, for any one crusher the throughput or production capacity of the crusher may not increase with an increase in the crusher speed. The production capacity of the crusher may even decrease slightly with a speed up in rotational speed.
The length of the stroke of the crusher, namely the difference between a maximum opening and a minimum opening at a given section through the space between the head and the bowl, does have an effect on the throughput of the crusher. The stroke length is typically established by the design of the crusher components, such as the amount of eccentricity in a camming member or sleeve which transforms rotational motion of a drive member into the desirable, gyrational motion of the crusher head. A cone crusher of a certain size when equipped with an eccentric member with increased eccentricity with respect to that of an original eccentric member, may show a marked increase in production capacity. A corresponding increase in the drive power or the rotational speed of the drive member may increase the power input to the crusher to accommodate the increased crushing action for a correspondingly improved production capacity. However, a comparatively longer stroke may not be optimally suited for relatively hard materials which require greater crushing force. Thus, typically a compromise stroke length is chosen which may not permit an ideal production rate in certain crushing operations.